1. Field of the Invention
The present invention relates generally to the fields of genetics, human genetics, and inherited metabolic disorders. More specifically, the present invention relates to an animal model for the study of G.sub.M1 -gangliosidosis.
2. Description of the Related Art
G.sub.M1 -gangliosidosis, a lysosomal storage disorder which affects brain and multiple systemic organs, is due to an autosomal recessively inherited deficiency of acid .beta.-galactosidase. This disease is clinically classified into three types based on, age at onset of clinical manifestations and on the degree of pathological changes. G.sub.M1 -gangliosidosis causes progressive neurologic and systemic impairments. Deficiency of acid .beta.-galactosidase is also associated with Morquio B disease, which is primarily a skeletal-connective tissue disorder without primary central nervous system involvement (Suzuki et al., 1995; Alroy et al., 1985; Kaye et al., 1997; Nishimoto et al., 1991).
Acid .beta.-galactosidase is a lysosomal hydrolase that cleaves .beta.-linked terminal galactosyl residues from gangliosides, glycoproteins, and glycosaminoglycans, as well as from a variety of artificial substrates (Morreau et al., 1991). A full-length cDNA for human .beta.-galactosidase has been cloned (Morreau et al., 1991; Oshma et al., 1988; Yamamoto et al., 1990), and point mutations and duplications in the human acid .beta.-galactosidase gene have been identified in patients with G.sub.M1 -gangliosidosis (Suzuki et al., 1995; Kaye et al., 1997; Nishimoto et al., 1991; Oshima et al., 1992; Yoshida et al., 1992; Isii et al., 1995; Yoshida et al., 1991; Oshima et al., 1991).
There is no specific treatment for G.sub.M1 -gangliosidosis. The potential of gene therapy as a therapeutic approach for several lysosomal storage diseases is now under consideration (Ahern-Rindell et al., 1996). However, prior to human application, these potential treatments must be established to be efficacious and nontoxic in experimental animals.
Animal models of genetic diseases similar to ones known to exist in humans are valuable and essential research tools. These models permit investigations of pathogenesis and the evaluation of potential therapeutic approaches. Canine G.sub.M1 -gangliosidosis is an excellent model for the human disease. The canine disease resembles the human disease genetically, clinically, biochemically, and pathologically (Suzuki et al., 1995; Ahern-Rindell et al., 1996).
To study the molecular pathology of canine G.sub.M1 -gangliosidosis and possibilities for gene therapy, knowledge of the full-length cDNA sequence for canine .beta.-galactosidase and its molecular defects in canine G.sub.M1 -gangliosidosis are essential. Canine G.sub.M1 -gangliosidosis has been described in several dog breeds, and the biochemical and enzymatic changes resulting from the disease have been studied (Alroy et al., 1985; Read et al., 1976; Rodriguez et al., 1982; Saunders et al., 1988; Alroy et al., 1992; Shell et al., 1989; Rittmann et al., 1980). However, the sequence of the full-length cDNA encoding canine .beta.-galactosidase has not been previously published. Furthermore, the molecular defects responsible for G.sub.M1 -gangliosidosis in these canine models have not been characterized (Suzuki et al., 1995). Only a partially deduced normal canine .beta.-galactosidase amino acid sequence lacking the 5' encoding region has been reported (Ahern-Rindell et al., 1996). However, the corresponding partial nucleotide sequence was not presented. Also, no nucleotide sequence data has been reported for the 5' encoding and untranslated regions as well as the 3' untranslated region. Although canine cDNA libraries were screened by the polymerase chain reaction, the 5' encoding region of the canine .beta.-galactosidase gene was not detected (Ahern-Rindell et al., 1996).
G.sub.M1 -gangliosidosis occurs in the Portuguese Water (PW) dogs. For breeding purposes, it is important to set carrier dogs apart. Although the enzyme assay has facilitated carrier diagnosis, enzymatic detection of carriers is not always reliable because varying degrees of overlap in enzyme activity can occur between normal homozygotes and heterozygous carriers (Suzuki et al., 1995). To solve this problem, it was necessary to isolate a normal full-length cDNA encoding the canine acid .beta.-galactosidase and search for the molecular defects which causes canine G.sub.M1 -gangliosidosis.
The prior art is deficient in the lack of a normal full-length cDNA encoding the canine acid .beta.-galactosidase, methods of screening for the molecular defects which causes G.sub.M1 -gangliosidosis, and an animal model for the study of the molecular mechanisms of G.sub.M1 -gangliosidosis and other lysosomal storage disorders. The present invention fulfills these longstanding needs and desires in the art.